Brachial Plexus is a network of nerves in the shoulder which is responsible for sensory and motor activity of the upper extremity. It is covered by the axillary sheath which is an extension of prevertebral fascia.
Brachial plexus includes Roots, Trunks, Divisions, Cords and Branches. We can remember these from the mnemonic RT (Arti) Drinks Cold Beer.
Roots of the Brachial plexus include C5, C6, C7, C8, T1.They arise from the spinal cord.
Trunks are present in the neck. There are 3 trunks-
Upper trunk (has root value C5 C6)
Middle trunk (has root value C7) and
Lower trunk (has root value C5 C8 T1)
Divisions are present behind the clavicle. There are two Divisions:
Anterior Division- will form the Lateral and medial cords (which will supply flexors).
Posterior Division- will form the posterior cord (which will supply extensors).
Cords are present in the axilla. There are 3 cords:
Posterior cord: is formed by all 3 posterior divisions.
Lateral cord: is formed by anterior divisions of upper and middle trunks.
Medial cord: formed by anterior division of lower trunk.
Branches are present in the axilla. In the brachial plexus, branches are given from the Roots, Upper trunk, Lateral cord, Medial cord and the Posterior cord.
Branches from the Roots:
- Dorsal Scapular Nerve (C5)
- Long Thoracic nerve of Bell/ Nerve to Serratus anterior (C5 C6 C7)- (This nerve is obviously long because it comes all the way from the root)
Branches from Upper trunk: (all have root value C5 C6)
- Suprascapular nerve (C5 C6)
- Nerve to Subclavius (C5 C6)
Branches from Lateral cord: (LML) (all have root value C5 C6 C7)
- Lateral Pectoral nerve (C5 C6 C7)
- Musculocutaneous nerve (C5 C6 C7)
- Lateral root of Median nerve (C5 C6 C7)
Branches from Medial cord: (M4U)
All have root values (C8 T1), except Ulnar nerve which receives additional fibres from C7 i.e. from the Lateral root of median nerve.
- Medial Pectoral nerve (C8 T1)
- Medial root of Median nerve (C8 T1)
- Medial cutaneous nerve of arm (C8 T1)
- Medial cutaneous nerve of forearm (C8 T1)
- Ulnar nerve (C7 C8 T1)
Branches from Posterior cord:(STARS)
- Upper Subscapular nerve (C5 C6)
- Thoracodorsal nerve (C6 C7 C8)
- Axillary nerve (C5 C6)
- Radial nerve (C5-T1) –Radial nerve is the largest branch of the Brachial plexus. It receives fibres from all the roots of the brachial plexus.
- Lower Subscapular nerve (C5 C6)